8 mins
Use of dermal fillers in atrophic acne scarring
Acne vulgaris is a chronic skin disease characterised by the A occurrence of skin lesions such as open and closed comedones, pustules, papules, and cysts.1
More than 80% of adolescents, 50–60% of women aged 20–25 years, and 12% of women over 25 suffer from acne. Factors that cause the disease include abnormal keratinisation of the pilosebaceous canal, increased sebum production, bacterial colonisation, and inflammatory and hormonal disorders of the skin.2
Acne scarring is a relatively common outcome of acute acne, with an estimate of 80% of acne scars being atrophic, with ice pick scars at 60%, boxcar scars at 25%, and rolled scars at 15%.3
Acne is characterised by follicular hyperkeratinisation and sebum overproduction, mediated by androgens in the pilosebaceous unit. The bacterium P. acnes proliferates in this situation, potentially triggering an inflammatory response which can lead to scarring. There is a higher risk of scarring with a prolonged inflammatory response and unbalanced ratio of matrix metalloproteinases (MMPs) to tissue inhibitors of MMPs (TIMPs) during the extracellular matrix remodelling (ECM) process.4
Acne scarring is challenging to treat, therefore prevention of scars by early aggressive treatment to reduce inflammation is key and sadly often ignored by patients and physicians. There is evidence that the use of retinoids is helpful in reducing the inflammation. Oral retinoids are more effective than antibiotics in the prevention of acne scarring5 and topical retinoids may also play a role in prevention.6
TYPES OF ACNE SCAR
Ice pick scars are deep, narrow, and can reach the border of the dermis with the subcutaneous tissue. They have sharp edges, a width of not more than 2mm, and a V-shaped cross-section with a narrowing deep into the skin. Boxcar scars are oval or round, but quite wide and flat, and resemble the letter U or a square. Their edges are well marked and have a demarcated edge. They are usually 0.1–0.5mm deep and 1.5–4mm wide. They can combine to form clusters. Boxcar scars have the cross-section of the letter M, while rolling scars are the largest of all types and can reach a diameter of 5mm.7
TREATMENT OF ACNE SCARS
The treatment of acne scars is dependent on the type of scar, the extent and severity, together with the downtime and preferences of patients and clinicians. There is no consensus for the best treatment regime, but most clinicians agree that treatment results are best with a combination of therapies for a longer period. Lasers, both ablative and nonablative, radiofrequency (RF) and standard microneedling, the chemical reconstruction of skin scars using trichloroacetic acid (TCA Cross), peels, subcision, punch excision and platelet-rich plasma (PRP) all have evidence of success in treating scars. This article focusses on the use of injectable substances for the improvement of acne scars.
Injectable substances can be divided into hyaluronic acids (HA) and collagen stimulators such as polylactic acid (PLLA), calcium hydroxyapatite (CaH) and polymethyl methacrylate (PMMA).
These treatments are readily available and easy to administer, and they appear to have a good side-effect profile.
HA DERMAL FILLERS
It is quite difficult to conclude what type of HA filler is most suitable and which technique is best due the terminology and design of various studies. Mehrabi, Joseph et al. (2023)8 compared a traditional crosslinked HA filler with a low molecular weight, non-cross-linked HA and found differences in initial results, but good longer term results treating acne scars, although they did not state what type of scar they treated.
Another study using a cross-linked HA injecting in the dermis until it raised a bleb, which was massaged flat, showed a good improvement in rolling acne scars. Another study using a modified tower technique and high lift HA achieved high patient satisfaction.9 A review by Abdel Hay R., Shalaby K., Zaher H., et al. in 201610 noted no difference in adverse events following dermal filler injection for acne scars compared with placebo.
The goal of treatment is to lift the scar and improve skin quality both generally and within the scars.
In conclusion, the best types of scars for dermal filler treatment are rolled scars, followed by boxcar scars. Volumising dermal fillers with greater cross-linking are more likely to provide volume, but are better injected in the deep dermis or deeper, as superficial injection may create a lump which is more difficult to flatten, and a modified tower technique may be useful. Less cross-linked fillers can be injected superficially but provide less lift. The problem with HA fillers is that they are not long lasting and create less collagen11 compared with other products such as PLLA and CaH, requiring more frequent multiple injections over time.
I conclude that HA fillers are best reserved for shallow rolled or boxcar scars.
CAH FILLERS
Longer lasting than HA filler, CaH fillers have shown good results in studies of acne scars.12 Another study using diluted CaH in cross hatched lines with micro-focussed high intensity focussed ultrasound (HIFU) showed good results with no adverse issues.13 Another found CaH just as good as monotherapy.14
Other studies15 found a combination of subcision and CaH helpful in rolled and boxcar scars, but not icepick scars.
PLLA FILLERS
PLLA has been shown to have clinical benefits for up to two years.16 Beer (2007)17 found that shallow broad scars respond well to PLLA but required seven sessions. Sapra S., Stewart JA., Mraud K., Schupp R. (2015)18 showed excellent results (44% excellent patient satisfaction) from three sessions of PLLA in rolled acne scars with only one nodule formed.
PLLA is safe if injected in the deep dermis or deeper, and is effective in long-term improvement of rolled and shallower boxcar scars. It is not effective in ice pick scars. It is superior to HA due to its longevity.
PMMA FILLER
Joseph et al. (2019)19 found improved results in 90% after seven months with PMMA for full face acne treatment with minimal side effects. Solomon P., et al. (2021)20 found it to be a safe product over multiple applications. Another study by the US Food and Drug Administration in 201421 found good efficacy and safety in the treatment of acne scars.
NEW COMBINATION FILLERS
HA/CaH and HA/PLLA gels have recently become available, and these theoretically could be useful in treating acne scarring.
CONCLUSION
Atrophic acne scarring is challenging to treat and requires a combination of treatments to obtain the best results. Given the current research, rolling scars respond best to injectable treatments, followed by shallow boxcar scars. Longer acting fillers such as CaH, poly-d-lactic acid and PMMA are best suited to treating these scars. Injection methods vary, but need to be at least deep dermal, and can be global or more localised. With correct techniques, these products appear to have minimal side effects and reasonable efficacy. However, current research is as yet inadequate to determine best practice.
REFERENCES
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